1. Field of the Invention
The present invention relates to a process for fabricating a semiconductor device, more specifically the process including the step of in-situ cleaning a plasma treatment chamber. For example, in fabrication of a semiconductor device such as an MOS or bipolar transistor, an oxide layer is clung onto the inner surface of a plasma CVD apparatus, and the oxide layer can be in-situ removed in the plasma reaction chamber at a high rate.
2. Description of the Related Art
Recently, fabrication of a semiconductor LSI often includes a process for depositing an oxide onto a wafer by plasma-enhanced CVD in a plasma reaction chamber.
Nevertheless, such plasma-enhanced CVD for depositing an oxide layer results in clinging an oxide onto the plasma reaction chamber, which oxide layer may be a cause to form particles during the later deposition and should be removed. This removal is done by wet or dry cleaning. The wet cleaning requires disassemble of the plasma reaction chamber and it takes a long time to completely remove the oxide layer by immersing the disassembled parts of the chamber. Accordingly, dry cleaning treatment has attracted attention since it allows a higher speed treatment. In such a dry cleaning process, NF.sub.3, gas plasma treatment is utilized under the conditions of a pressure of 1 Torr, a power of 800 W and a microwave frequency of 2.45 GHz.
This dry cleaning treatment with NF.sub.3 gas plasma still has a certain limitation in its cleaning speed depending on the rate of its chemical reaction and therefore can not comply with recent demands for a faster cleaning treatment.
The object of the present invention is therefore to provide a process for fabricating a semiconductor device in which an oxide layer clung inside a plasma treatment chamber during plasma CVD, etc. can be removed at a high rate.